Stem Cells/Transcript
Transcript Text reads: The Mysteries of Life with Tim & Moby. A man named Tim and a robot named Moby are sitting at a table staring at a block of clay. MOBY: Beep? TIM: I’m not sure. I was thinking of making a T. rex. Tim concentrates while working the clay, and then frowns. The clay has been formed, but does not look like a T. rex. MOBY: Beep! Moby hands Tim an envelope. TIM: Well, let’s see if you can do any better! Tim reads the letter. TIM: Dear Tim & Moby, I've been hearing a lot about stem cells in the news. What are they? Thanks, Turtle. First off, cells are the building blocks of life. The human body is made up of about 75 trillion tiny cells. An illustration shows a multi-layered cluster of cells. Each cell is a round object with a variety of features inside. The cells are packed closely to each other so that they touch. The scene zooms out to show that the cluster repeats over a large volume, continuing out each edge of the scene. TIM: There are 220 different kinds in your body—bone cells, nerve cells, red blood cells, and many more. These cells are specialized, meaning that they have their own specific jobs to do. Drawings of each type of cell are colored in as Tim says their name. • Bone cell: a round white cell with three concentric circular layers. There is a hole in the middle of the cell • Nerve Cell: A long, gray cell with many branches and sub-branches. • Red Blood Cell: A red, round cell with a divot in the center. TIM: Like, a brain cell is a brain cell—it can never change into a skin cell, or a white blood cell, or any other type of cell. Tim and Moby are sitting at the table. Moby is frowning and his arms are crossed. MOBY: Beep. TIM: I was getting to that. Stem cells are unspecialized. They don’t have any one job in particular; they just divide and make more stem cells. The video shows a single stem cell. It is a round cell with one visible round feature on the inside occupying most of the volume of the cell. As Tim speaks, the stem cell divides into two identical stem cells, and then each of those divide again into identical cells. Four stem cells are shown. TIM: But more importantly, stem cells can change into other kinds of cells. Pretty cool, huh? Three of the stem cells change into one of each of the previously seen cell types: a bone cell, a nerve cell, and a red blood cell. The fourth stem cell does not change. MOBY: Beep! Moby smiles. TIM: In fact, all of us started out as a single stem cell called a “zygote.” It forms when a sperm cell fertilizes an egg cell. The video shows a sperm cell approaching an egg cell from the edge of the scene. The egg cell is large and round and has a visible central feature. The sperm cell is small, and shaped like an oval, with a long tail wiggling behind it. It also has a single central feature that resembles the one inside the egg. The head of the sperm cell enters the egg and fades away, leaving only the central feature, which continues into the egg and merges with the egg’s central feature. A thicker outer layer forms outside the egg cell. TIM: Zygotes, and the first few cells they divide into, are “totipotent.” They have the potential to become any cell in the body. The zygote divides by twos into multiple new cells that all resemble smaller versions of the original zygote. They remain clustered in a small ball. TIM: But as the embryo’s cells continue to divide, they begin to specialize. In humans and other mammals, they eventually form a hollow ball with a cluster of cells inside. The embryo turns purple, larger than it was, and still roughly ball-shaped. TIM: These are the embryonic stem cells you’ve probably heard about in the news. A cross section of the purple cluster shows that it is a hollow shell made of a single layer of cells. Inside the hollow purple ball is a cluster of embryonic stem cells. TIM: They’re “pluripotent,” which means they can become almost any kind of cell in the body. Three of the embryonic stem cells are arranged in a line. The first turns into an eyeball. The second turns into a heart. The third turns into a tooth. TIM: The one thing they can’t form is that ball of cells that surrounds them! The cross section of the hollow purple ball of cells fades out and is replaced by the complete ball. TIM: Anyway, scientists can take the stem cells and grow “lines” of them in the lab, making them divide over and over again. These lines could help cure millions of people suffering from all kinds of problems, like Parkinson’s disease and diabetes. The video shows Tim and Moby sitting at the table. TIM: One day, people with heart disease could get brand new hearts, and paralyzed people could walk again with new spinal cords! The screen splits. On the left is a beating heart. On the right is a woman sitting in a wheelchair. The woman’s shadow stands up out of the wheelchair. MOBY: Beep. Moby frowns. TIM: Right. Gathering embryonic stem cells is controversial. To get them, doctors must destroy the embryo. The ball of purple cells is labeled “embryo.” It darkens while Tim is speaking. TIM: A lot of people believe that’s the same thing as ending a human life. The video shows protestors holding signs in front of a courthouse. Text reads: EMBRYOS ARE NOT DISPOSABLE. Text reads: PROTECT LIFE. TIM: Others argue that these cell clusters aren’t the same as human beings, and that doctors only gather cells that were going to be destroyed anyway. Either way, scientists are researching other ways to gather stem cells. Tim and Moby are sitting at the table. MOBY: Beep? TIM: Well, one avenue of research involves adult stem cells. All people have these cells in their bodies. They can be found in the liver, brain, bone marrow, skin, and certain kinds of muscle. Example images of each of these organs appear as Tim is saying them. • liver: a smooth lobe-shaped organ in three sections • brain: a round organ made up of many folded and ridged sections • bone marrow: the inside of a bone. • skin: a patch of hairy skin. • muscle: a long band of fibrous material. TIM: Our bodies use adult stem cells to repair damaged tissue. A close-up of the liver changes from a darker to brighter shade. TIM: Unfortunately, adult stem cells aren’t as flexible as embryonic ones. They’re also more difficult to grow in laboratories. And scientists still aren’t sure if adult stem cells from, say, the liver, can turn into anything but liver cells. The brighter shaded liver is initially on screen. As Tim speaks, an eyeball, a heart and a kidney appear, each labeled with a question mark. TIM: However, there have been a number of advances in recent years. MOBY: Beep? TIM: Well, the biggest development involves something called induced pluripotent stem cells. Basically, scientists have been able to “de-program” adult stem cells so that they act more like embryonic stem cells. Four people wearing lab coats are sitting at long benches, looking through microscopes. TIM: But this technology is very new, and a lot more work has to be done before it can be used to help cure diseases. Researchers have also discovered another source of stem cells: the umbilical cord and placenta, which connect babies to their mothers in the womb. A developing fetus is in a womb. The womb is illustrated as a sac surrounding the fetus. The placenta is a large red form on one side of the womb. The fetus is connected to the placenta by the umbilical cord. TIM: If doctors gather a baby’s “cord blood” from one of these locations right after she’s born, the stem cells inside it might help her later in life. A syringe with a needle is drawing blood from an umbilical cord. TIM: Cord blood stem cells have proven useful in fighting certain blood disorders. And there’s a good chance that someday, they might help with other diseases and conditions. A man is lying in a hospital bed with monitoring equipment and an I V drip next to him. A medical worker is next to his bed, reading a chart. TIM: But just like induced pluripotent stem cells, there’s still a lot of research to be done on them. Tim and Moby are at the table with the not-so accurate clay model of a T. rex. MOBY: Beep? TIM: Anyway, you finished with that clay? MOBY: Beep! Moby glances down at the table. The clay T. Rex has been reshaped to a scale model of Rodin’s “The Thinker,” a sculpture of a naked man sitting with his hand under his chin, appearing to be deep in thought. TIM: Oh, that’s real original.Category:BrainPOP Transcripts